On the Active Users page, select the name of the person you want to edit.

On the right, in the Username / Email Aliases row, choose Edit.

In the Alias box, type the first part of the new email address. If you added your own domain to Office 365, you can choose the domain for the new email alias by using the drop-down list. Then choose Add.

IMPORTANT:

If you get the error message "A parameter cannot be found that matches parameter name 'EmailAddresses" it means that it’s taking a bit longer for Office 365 to finish setting up your tenant, or your custom domain if you recently added one. The setup process can take up to 4 hours to complete. Wait a while so the setup process has time to finish, and then try again. If the problem persists, call Support and they will do a full sync for you.

If you get the error message "We're sorry, the user couldn't be edited. Review the user information and try again." it means you aren't an Office 365 global admin and you don't have permissions to change the user name.

Choose Set as Primary for the email address that you want to set as the primary email address for that person.

You'll only see this option if you're an Office 365 global admin. If you don't see the option, you don't have permissions to change a user's name and primary email address.

You'll see a big yellow warning that you're about to change the person's sign-in information. Choose Save, then Close.

Tell the person the following information:

What their new username is. They’ll need it to sign in to Office 365.

If they are using Skype for Business Online, tell them they will need to reschedule any Skype for Business Online meetings that they organized, and that they will need to tell their external contacts to update the old contact information.

If their password changed too, tell them that they will be prompted to enter the new password on their mobile device, or it won't sync.

Change a user's display name

Next to the person's display name, choose Edit.

Type a new name for the person and then choose Save.

If you get the error message "We're sorry, the user couldn't be edited. Review the user information and try again." it means you aren't an Office 365 global admin and you don't have permissions to change the user name.

Did you get "A parameter cannot be found that matches parameter name 'EmailAddresses"?

If you get the error message "A parameter cannot be found that matches parameter name 'EmailAddresses" it means that it’s taking a bit longer for Office 365 to finish setting up your tenant, or your custom domain if you recently added one. The setup process can take up to 4 hours to complete. Wait a while so the set up process has time to finish, and then try again. If the problem persists, call Support and they will do a full sync for you.

Did you get "We're sorry, the user couldn't be edited. Review the user information and try again"?

If you get the error message "We're sorry, the user couldn't be edited. Review the user information and try again." it means you aren't an Office 365 global admin and you don't have permissions to change the user name. Find the Office 365 global admin in your business and ask them to make the change.

More information on changing or adding email addresses

A person's previous primary email address is retained as an additional email address. We strongly recommend that you don't remove the old email address.

Some people will likely continue to send email to the person's old email address and deleting it may result in NDR failures. Office 365 will automatically route it to the new one. Also, do not reuse old SMTP email addresses and apply them to new accounts. This can also cause NDR failures or delivery to an unintended mailbox.

It might take up to 24 hours for this change to take effect across all services. After the change has taken effect, the person will have to sign in to Outlook, Skype for Business and SharePoint with their updated username, so be sure to tell them about this change.

If they are using Exchange Online or if their Office 365 account is linked with your organization's on-premises Exchange environment, you may see this error when you try to change a username and email address: "This user is synchronized with your local Active Directory. Some details can be edited only through your local Active Directory."

This is due to the Microsoft Online Email Routing Address (MOERA). The MOERA is constructed from the person's userPrincipalName attribute in Active Directory and is automatically assigned to the cloud account during the initial sync and once created, it cannot be modified or removed in Office 365. You can subsequently change the username in the Active Directory, but it will not change the MOERA and you may run into issues displaying the newly changed name in the Global Address List.